Electronic device for regulating and controlling the delivery of yarn coming from feed units of textile machines

ABSTRACT

An electronic device for regulating and controlling the delivery of yarn ( 18 ) coming from feed units of textile machines, which is designed to vary the r.p.m. of a d.c. brushless motor ( 23 ) so as to keep it as synchronized as possible, according to an adjustable scale factor, with the speed of the textile machine served; the device comprises the d.c. brushless motor ( 23 ) and an electronic circuit based upon operation of a microcontroller ( 21 ) that is able to control the r.p.m. of the motor ( 23 ) and the currents (I 1 , I 2 , I 3 ) in the phases of the aforesaid motor ( 23 ).

The present invention relates to an electronic device for regulating andcontrolling the delivery of yarn coming from feed units of textilemachines.

Yarn-feed reels of a textile machine are usually set on the top frame ofthe machine or on a side reel-frame. In this connection, the sidereel-frame occupies more space but enables an increase in the number ofyarn feeds, the possibility of resorting to double feed at each drop,and the possibility of changing the empty reels more easily and rapidly.

On textile machines with rotating skirts, the reel-frame is fixed to,and set in continuous rotation with, the skirts themselves.

In any case, prior to arriving at the needles, the yarn follows a ratherlong path to give the machine time to stop before a possible broken endgets caught up.

FIG. 1 shows a typical example of path of the yarn, designated by 18,which reels off the bobbin or reel 10, passes within a firstthread-tightener 11 and in an arrest device 12, which operates both inthe case of breaking of the thread and in the case of excess tension.The thread-tightener 11 must be located as far as possible from theneedles of the textile machine for the reasons mentioned above.

There follows a second thread-tightener 13 used for adjusting thetension to pre-set values, as well as a possible system 14 forcontrolling feed of the yarn.

Finally, there is envisaged the installation of a machine arrest 15,which acts in the event of breaking of the yarn 18.

In particular, on the most recent circular knitting machines, control ofthe feed is extremely important. For this reason, positive feeders canbe used, which release to the needles a length of yarn that is asconstant as possible in time, or accumulation feeders are provided,which maintain the tension of the yarn as constant as possible.

The positive feeder most widely used at the moment is the ribbon feeder(see FIG. 2 attached), whereby a ribbon 16 runs all around thecircumference 17, at each drop. The yarn 18 passes between the ribbon 16and the wheel 19 and acquires the speed of the former so as to obtain amore uniform fabric, regulating the absorption on all the drops withjust one operation in so far as, necessarily, all the threads of yarn 18are fed the individual drops at the same speed.

Alternatively, control of the positive feeders of the yarn can beobtained by means of interchangeable gears located in a specialgear-case and by expandable pulleys with manual adjustment.

Adjustment of the expandable pulleys is carried out by slackening abelt, using a belt-tensioner, and then by releasing a ring nut using apin provided so as to gain access to the plate of the pulley. It is thuspossible to adjust the diameter by rotating the aforesaid plate of thepulley, which is provided with reference marks and, finally, tore-tighten the ring nut.

Upon request, further gears are available for different feeds of theyarn and arrangements of the textile machines to accept one-way ormultiple-way positive heads, as well as different sizes of the belts.

A purpose of the present invention is therefore to overcome thedrawbacks mentioned above and, in particular, to provide an electronicdevice for regulating and controlling delivery of yarn coming from feedunits of textile machines which will enable adjustment of the deliveryof yarn by varying the speed of a d.c. motor so as to keep it assynchronized as possible, according to an adjustable scale factor, withthe speed of the textile machine served.

Another purpose of the present invention is to provide an electronicdevice for regulating and controlling delivery of yarn coming from feedunits of textile machines which does not involve the use of complexand/or particularly costly technologies and which enables substantialreduction of processing times and of losses in productivity as comparedto known techniques by managing the production processes in a moreappropriate way.

The above and other purposes are achieved by an electronic device forregulating and controlling delivery of yarn coming from feed units oftextile machines according to claim 1, to which the reader is referredfor reasons of brevity.

Advantageously, the regulation device according to the invention is madeup of a d.c. brushless motor and an electronic circuit, which comprisesa microcontroller that is able to control the r.p.m. of the motor andthe currents in the phases.

An encoder, connected to the axis of rotation of the motor, enablesdetection of the r.p.m. and of the incremental position of the motor andcomparison of said quantities with the speed of rotation and of theincremental position of the machine, this information being derived fromthe signals received from the main reference encoder.

The device can be remotely controlled and programmed by means of anasynchronous serial interface of the RS485 half-duplex type, with whichit is equipped.

Also provided are two inputs for the connection of sensors for arrestingthe yarn, of the Hall-effect type, an input available for a manualcontrol for excluding arrest of the yarn, an output of an open-collectortype for remote signalling of a condition of collective arrest, and someLEDs for remote display of a state of arrest.

A single 24-V d.c. supply voltage is provided.

Further purposes and advantages of the present invention will emergeclearly from the ensuing description and from the attached schematicdrawings, which are provided purely by way of explanatory andnon-limiting example of embodiment, in which:

FIG. 1 shows the path of the yarn which is reeling off a reel, in ageneric textile machine belonging to the state of the art;

FIG. 2 is a partial perspective view of a ribbon-type positive feeder,which can be used for delivery of yarn in known textile machines; and

FIG. 3 is a block diagram of an electronic device for regulatingdelivery of yarn coming from a feed unit of textile machines accordingto the present invention.

With particular reference to the FIG. 3, the main functional elements ofthe electronic device for regulating and controlling the delivery ofyarn according to the present invention are represented by amicrocontroller designated by 21, a signal and power analog sectiondesignated by 22, and a d.c. brushless motor 23 associated to aHall-effect local encoder 27.

The microcontroller 21 receives from a buffer 24 of a serial line of theRS485 type the configuration commands, and transmits, upon command, theinformation regarding the current situation, driving the signallingoutputs accordingly.

The above information is acquired by reading the logic signals comingfrom a set of sensors 25 for arrest of the yarn or from a manual command20 for excluding said arrest by reading signals generated by a referenceencoder 26 and comparing said signals with the signals coming from theencoder 27 fitted on the shaft of the motor 23.

Also present is an output of an open-collector type designated by 50which can be used for remote signalling of a condition of collectivearrest, and a number of LEDs 51 for remote display of a state of machinearrest.

By taking into account just the advance pulses, the microcontroller 21calculates the difference between the number of pulses received from thetwo encoders 26, 27, either incrementing or decrementing the count.

The instantaneous value totalized by the counter, with appropriatecorrective factors that can be modified by manual commands issued on theserial line, is used as reference of speed of the analog and powersection 22.

The output 40 of the microcontroller 21 is of the PWM type, which can betransformed into a voltage level thanks to the presence of a low-passfilter 28.

In addition, the microcontroller 21 sends further commands, designatedas a whole by 29 in FIG. 3, to the analog section 22 for switching ofthe phases, the said commands being defined according to the dedicateddevice used for controlling the current in the phases of the d.c.brushless motor 23. In particular, the said commands may consist simplyof a dynamic-brake command issued when it is desired to stop the motor23, or directly of the commands for enabling the three branches of thepower bridge, acquired by the microcontroller 21 by decoding the signalsH1, H2, H3 for the position of the rotor of the motor 23 with respect tothe stator. The analog and power section 22 is made up of a signalportion and a power portion. The signal portion receives the logicsignals H1, H2, H3 or CHA, CHB produced by one or more encoders 27 ofthe motor 23 and, from these, via a frequency/voltage converter 39,derives a unidirectional tachimetric signal 41, of an analog type, whichis compared with the speed reference 40 generated by the microcontroller21 and processed by the low-pass filter 28.

The choice between the logic signals H1, H2, H3 or CHA, CHB depends uponthe number of pulses per rev for a uniform movement of the motor 23 atlow speed. In fact, exploiting all the signal edges, in the first case(using the signals H1, H2, H3) twelve pulses per rev are obtained,whereas, in the second case (using the signals CHA, CHB), with a 32-polemagnetized wheel, sixty-four pulses are obtained per rev.

The difference (signal 42) between the signals 40 and 41, appropriatelyfiltered by the low-pass filter 30, is used as current reference for thenext stage, designated as a whole by 31 in FIG. 3.

Here it is compared with the signal 43 coming from the shunt resistor32, which is proportional to the current circulating in the phases ofthe motor 23, generating the control signal 44 for the PWM modulator 33.The output of the latter (designated by 45) fixes the turning-on andturning-off times for the drivers 34 of the MOSFETs 46 of the powerbridge 35, whilst the other control signals 29 received from the drivers34 determine which MOSFETs 46 in each branch of the power bridge 35 mustswitch and which must remain turned off.

The above control signals 29 may all come from the microcontroller 21 orelse may be derived, in part, from the signals H1, H2, H3 for theposition of the rotor of the motor 23. This depends upon the dedicateddevice used for controlling the current in the phases of the d.c.brushless motor 23.

The three-phase power bridge 35 is normally made up of six MOSFETs,designated by 46, and by six freewheeling diodes, designated by 47, andthe three branches 48 of the bridge 35 generate the three currents I1,I2, I3 circulating in the three phases of the motor 23 (a maximumcurrent value per phase of approximately 1.5 A is reached).

In addition, since the motor is a d.c. brushless motor, at each instantit is possible to energize the three windings so as to obtain advance ofthe rotor according to the current position thereof. With the threecanonical combinations, in one direction of use of the windings of themotor, which carry out energizing of just two windings at a time, it ispossible to exploit a further three intermediate switching combinations,in which, alternately, one winding is connected to the positive side ofthe supply bus and the other two windings, simultaneously, to thenegative side of the supply bus, or vice versa. There are thus obtainedsix switches for each pole of the motor, to which there correspond sixequidistant angular advances of the rotor.

The motor assembly of the entire electronic regulation and controldevice, in addition to the motor 23 proper (for which the model BLDC48“Premotec” may be used), comprises an encoder 37 for detecting theposition of the rotor of the motor 23, which generates the signals H1,H2, H3, and the local encoder 27, both of which are fitted on the shaftof the motor 23.

The local encoder 27 may be obtained using a magnetized wheel having adiameter that is compatible with the dimensions of the motor 23 and isequipped with thirty-two magnetic poles. For reading, pairs ofHall-effect sensors are preferably used so as to enable discriminationof the direction of revolution, whilst the signals generated may be theclassic channels A, B (signal CHB), or else a clock having a frequencyproportional to the r.p.m. of the motor 23 (which reaches a maximum ofapproximately 10 000 r.p.m.) and a bit for the direction of revolution(signal CHA).

The local encoder 27 may then be eliminated if the signals H1, H2, H3enable a sufficiently regular movement to be obtained at a low r.p.m.

Finally, the electronic device comprises a local power supply 38 of alinear type, which enables a reduced voltage of +5 V for supplyingelectric power to the logic 22, as well as a possible intermediatevoltage for the drivers 34 of the power bridge 35, to be obtaineddirectly from the 24-volt supply voltage V. The power of the bridge andthe value of the said intermediate voltage depend upon thecharacteristics of the dedicated device used for controlling the currentin the phases of the brushless motor 23.

Furthermore, an electrolytic capacitor of adequate capacitance provideslocal coverage of the current peaks absorbed by the motor 23 andinitially absorbs the voltage peaks during deceleration, whilst theremaining energy must be absorbed by the 24-V d.c. supply bus 49 anddissipated upstream of the power supply 38.

The characteristics of the electronic device for regulating andcontrolling the delivery of yarn coming from feed units of textilemachines, which forms the subject of the present invention, as well asthe advantages, emerge clearly from the foregoing description.

Finally, it is clear that numerous variations may be made to theelectronic regulation and control device referred to herein, withoutthereby departing from the principles of novelty inherent in theinventive idea. It is likewise clear that, in the practicalimplementation of the invention, the materials, shapes and dimensions ofthe items illustrated may be any whatsoever according to therequirements, and may be replaced with other technically equivalentones.

1. Electronic device for regulating and controlling the delivery of yarn(18) coming from yarn storage units of textile machines, said electronicdevice comprising at least one local power supply (38) for supplyingelectric power and means for varying the r.p.m. of a motor (23) so as tokeep it synchronised, according to an adjustable scale factor, with thespeed of the textile machine to which said device is connected, whereinsaid motor (23) is, a D.C. brushless motor and said means for varyingthe r.p.m. of the motor (23) comprise an electronic circuit, whichincludes at least one microcontroller (21) that controls the r.p.m. ofthe motor (23) and the currents (I1, I2, I3) circulating in the phasesof said motor (23), characterised in that said D.C. brushless motor hasthree windings, which can be powered at any time to let the rotor ofsaid motor (23) travel depending on a prefixed position of the rotor, sothat, with three combinations of use in one direction of said motorwindings, said combinations providing for just two windings to bepowered at a time, three further intermediate switching combinations canbe utilised, wherein, alternately, one winding is connected to thepositive pole of said power supply (38) and the other two windings aresimultaneously connected to the negative pole of said power supply (38),or vice versa, to obtain six switchings for each motor polecorresponding to six equidistant angular shifts of said rotor. 2.Electronic device as claimed in claim 1, characterised in that saidelectronic circuit comprises at least one first encoding element (27),connected to the axis of rotation of said motor (23), enabling detectionof the r.p.m. and of the incremental position of the motor (23) andenabling comparison of said motor r.p.m. and said motor incrementalposition with the rotation speed and the incremental position of thetextile machine, said rotation speed and incremental position of thetextile machine being derived from signals received from at least onesecond reference encoding element (26).
 3. Electronic device as claimedin claim 1, characterised in that at least one asynchronous serialinterface is provided for enabling, by means of a buffer (24), remotecontrol and programming of the electronic device.
 4. Electronic deviceas claimed in claim 2, characterised in that said microcontroller (21)is provided for calculating the difference between the number of pulsesreceived from said first and second encoding elements (26, 27), eitherincrementing or decrementing the count, so that an instantaneous value,which can be obtained by means of suitable corrective factors that canbe modified by manual commands, is used as a speed reference of ananalogue and power section (22) of said electronic circuit. 5.Electronic device as claimed in claim 4, characterised in that at leastone reference speed signal (40) at the output of said microcontroller(21) can be converted into a voltage level by means of a low-pass filter(28), said microcontroller (21) being also used for sending to saidanalogue and power section (22) further control signals (29) forswitching the phases of said motor (23), said control signals beingdefined on the basis of a predetermined device used for controlling saidcurrents (I1, I2, I3) circulating in the phases of said motor (23). 6.Electronic device as claimed in claim 5, characterised in that saidanalogue and power section (22) comprises a signal portion, whichreceives one set of logic signals (H1, H2, H3; CHA, CHB) produced bysaid first encoding element (27) of the motor (23), said signal portionderiving from said logic signals (H1, H2, H3; CHA, CHB), via aconverting device (39), a unidirectional tachometric signal (41), whichis compared with said speed reference signal (40) at the output of saidmicrocontroller (21).
 7. Electronic device as claimed in claim 6,characterised in that a signal representing the difference (42) betweensaid speed reference signal (40) and said tachometric signal (41) isfiltered and used as current reference signal for a subsequent stage(31) of said analogue and power section (22), wherein said differencesignal (42) is compared with a further signal (43), which isproportional to said currents (I1, I2, I3) circulating in the phases ofthe motor (23), to obtain a control signal (44) for a modulator device(33), the output (45) of which reveals the turning-on and turning-offtimes for a set of driving means (34, 46) of a power circuit (35), saidpower circuit (35) using said further control signals (29) for switchingthe phases of said motor (23), said control signals (29) coming fromsaid microcontroller (21) or being derived, at least partially, from aset of signals (H1, H2, H3) relating to the position of said rotor ofthe motor (23), said set of signals (H1, H2, H3) being provided byencoding means (37).